Packaging containers made of sheet metal with tear-open device

ABSTRACT

This disclosure relates to the formation of a weakening line defining an opening panel part of a container, the weakening line being formed by configurated dies having opposed portions which are aligned and other portions which are transversely misaligned whereby when the dies strike a panel, offsetting of a portion of the panel occurs together with a reduction in thickness of the panel in the area of die alignment. The die construction is one which is not readily subject to wear or damage.

United States Patent Baumeyer et al.

[ 51 Sept. 26, 1972 PACKAGING CONTAINERS MADE OF SHEET METAL WITH TEAR-OPEN DEVICE inventors: Martin Baumeyer; Luebeck Wilhelm Neben, both of Hamburg, Germany Assignee: Schmalbach-Lubeca-Werke,

Braunschweig, Germany Filed: Feb. 19. I971 Appl. No.: 116,823

Foreign Application Priority Data Feb. 21, 1970 Germany ..P 20 08 090.4

US. Cl. ..220/54, 220/27, 1 13/15 Int. Cl. ..B65d 17/24 Field of Search ..220/54, 27; 113/l5, 121

References Cited UNITED STATES PATENTS 5/1939 Fabrice ..1 13/15 A l2/l945 Beaton ..1i3/l5 A Primary ExaminerGeorge T. Hall Attorney-Diner, Brown, Ramik & Holt ABSTRACT 1 Claim; 4 l) rawingFlgnres i, E iln siii PATENTEnssrzs 1912 3.691827 INVENTUR MHRTIN BDUMiYER 5b WlLHELM NEBEN ATTORNEYS PACKAGING CONTAINERS MADE OF SHEET METAL WITH TEAR-OPEN DEVICE The invention relates to a packaging container with tear-open arrangement, preferably to a tear-open cover, whose recessed surface has a tear-open part surrounded by weakening lines, and to which tear-open part a pulling handle is secured with the pull handle extending above the recessed surface of the cover.

BACKGROUND OF THE INVENTION In the case of the processes used hitherto for producing the weakening lines limiting the thickness of the material locally, which processes have also been known as scoring, the weakening of the material in parts of containers, especially their covers, made of metal or of some such raw materials, are produced by placing the element on a support and a suitable stamping tool, such as a notching tool, is moved against the element. The actual weakening process is brought about by a local extrusion. The proper tools, generally speaking, are developed in the shape of a trapezoid or a wedge on their actual operating or effective surface. Correspondingly, the cross section of the weakening of the material of the element has a trapezoid or cuniform shape.

It is obvious in the case of the previously mentioned stamping-like or notching-like process that considerable operating pressures have to be used depending on the pertinent physical characteristics of the raw material. ln addition to the considerable expenditure of ener gy, the tool must be fabricated with the utmost precision. lt is therefore expensive. Furthermore, experience has shown that the tool has only a relatively short useful life, since its corners easily wear out and there is the danger that its edges are easily notched because of high shearing loads. Also, the tool must be aligned very exactly.

In summary, it turns out, therefore, that despite a good durability of weakening lines of this kind, in practice, that is to say in the proper field, there nevertheless are disadvantages connected with it.

Prior to the introduction of the initially mentioned packaging container with tear-open arrangement, packaging containers with tear-open lids were known on the market, in the case of which separate opening keys, preferably in the shape of turning keys, were added and had to be used. The weakening line of these containers were formed by the so-called technologically inaccurate term pressure slitting operation which in the packaging industry was also generally designated as Norwegian tear open". This type of for mation of weakening lines was characterized in that the middle part to be removed or loosened was produced by offsetting the material while decreasing the cross section in the area of transition of the ofi'setting. For reasons of the most simple assignment and use of tools, the offsetting was accomplished in such a way that the middle part that was to be removed or loosened lay toward the inside, this is pointing toward the inside of the container. This development of the offsetting toward the inside had the functional disadvantage that during the tearing open process or during rolling up of the middle part of the lid, which was accomplished toward the outside, an increased tear-open force was needed during the opening process in order to guide the outside edge of the tear part, which had been offset toward the inside, past the inside edge of the residual wall. This disadvantage, however, generally had no effect whatever on the opening function or the manner of opening by the consumer, since the pertinent factor (torque) resulting from the use of the key in connection with its shaping as a turning or lever element was so great that these additional forces could be compensated for without appreciable additional expenditure of force on the part of the operating individual.

An advantage that should not be underestimated of the just described so-called pressure slitting" lay in the fact that the tools required for producing the weakening lines were relatively simple in their structure and thus inexpensive and correspondingly the danger of wear was also slight and the danger of damage was as good as impossible, and in that no complicated alignment of these tools became necessary and therefore the entire production of this type of weakening lines was simplified and the corresponding lids became lower in regard to their production costs.

SUMMARY OF THE lNVENTION ln view of the disadvantages in regard to tools of the initially mentioned notching tools, which have a particularly negative effect especially in mass production today of tear-open covers, the task became imperative to find a way to avoid the above mentioned disadvantages while retaining the same reliability of the weakening lines in regard to the easy opening of the device. ln other words, the problem was to discover a development of the weakening lines, the production of which, from a manufacturing point of view, is not only simple, at least under no circumstances should it be any more complicated than the methods customary hitherto with the use of notching tools, but which, above all, will effectively avoid the disadvantages and problems shown in regard to tool techniques.

Surprisingly it has now been found that the disadvantages shown can be avoided through application of the previously mentioned pressure slitting" but a different way, that is, through the fact that the weakening lines are formed by a per se known offsetting of the raw material, for example the sheet metal, by a decrease in the cross section in the area of transition of offsetting, whereby the tear-open part that is to be removed is directed toward the outside in regard to the residual part of the wall. As a result of that, from the point of view of tool technique, the advantages will be achieved that the tool needed in this case is simpler and therefore cheaper, a time consuming alignment of the tool is not necessary to the degree as was necessary in the case of the tools customary utilized heretofore, damage to the tool will almost be entirely avoided, and the wear will be considerably less.

From the point of view of opening techniques, the weakening lines made in this manner are at least equally as reliable as those made heretofore, whereby the above mentioned disadvantages of an increased tear-open force will be eliminated in the case of the invention because of the guidance of the outside edge of the center part offset toward the inside in the case of the formerly customary pressure slitting" past the inside edge of the residual wall, through the fact that in this case the tear-open part to be removed is directed outwardly in relation to the residual part of the wall. Finally, in the case of stress from the outside, the new development is considerably more stable.

Another characteristic of the invention consists in this, that the width of the decrease in the cross section corresponds approximately to the thickness of the raw material, for example, the sheet metal.

The invention will be explained in more detail on the basis of an embodiment which is shown in the drawing.

FIG. I is a fragmentary plan view of a container lid with tear-open device in accordance with the invention.

FIG. 2 and 3 are enlarged fragmentary sectional views showing the details of customary weakening lines.

FIG. 4 is enlarged fragmentary sectional view showing the formation of the weakening lines according to the invention.

The present embodiment shows a conventional lid of an elongated oval shape, as used, for example, in the case of cans for the packaging of fish. This lid, as is well known, is connected with the body of the container through a seaming operation. The recessed surface 2 of lid 1 has a tear-open part 4 defined by a continuous weakening line 3, the tear-open part including a starting section 5 to which an essentially rigid tear-open handle 6 has been attached by means of a rivet 7.

Numeral 8 designates beads provided to facilitate the opening, while 9 designates the residual wall of the recessed surface 2 of lid 1 which will remain.

The previously described design has been known in principle and represents one of many possible designs which may be found on the market.

The presentations in section according to FIGS. 2 and 3 relate to the area A in the left-hand part of FIG. I and show the heretofore customary cross sectional shapes of the weakening lines 3. Thus, FIG. 2 shows a weakening line 3 having trapezoidal cross section. The notching tool in its effective area has been developed trapezoidally in a corresponding shape.

FIG. 3 shows a weakening line 3 of cuniform, for the production of which, in a correspondingly shaped tool is required. Both the previously mentioned designs are presently in use.

The design of the weakening line 3 according to the invention is shown in FIG. 4 which represents a cross section taken in the area B in the right-hand part of FIG. 1. As FIG. 4 clearly shows, the weakening line 3 has been formed by a deformation of the sheet metal with a decrease of the cross section in the area 30 of the deformation, whereby tear-open part 4 that is to be removed has been offset toward the outside of the container in relation to the residual part 9 of the wall. The transition area in this case is formed by compression of the material. The width of the decrease thickness area 3a of the cross section, as can be seen clearly in the drawing, corresponds approximately to the thickness of the sheet metal. The tools designated 10 for producing this weakening of the cross section are simple as is shown in FIG. 4. They have no edges shaped in such a way so as to be affected by wear so as to result in a varied notching.

It will be readily apparent from FIG. 4 that the dies 10 each includes a forming surface of which a part only defines the de ire weakening li ie and thgt s c djas 10 are transverse y 0 set. s a r su t, w en t e res engage opposite surfaces of the panel, the panel part 4 defined by the weakening line 3 is offset upwardly, as illustrated in FIG. 4 with respect to the remainder of the panel. That portion of the panel which is disposed between the aligned portions of the dies 10 is reduced in thickness over a relatively wide area, such area being generally equal to the thickness of the material of the panel, and there being no abrupt lines of rupture which would be subject to undue stressing and accidental rupture in the handling of the resultant container.

Although only a preferred embodiment of the invention has been specifically illustrated and described herein, it is to be understood that minor variations may be made in the invention without departing from the spirit and scope of the invention, as defined by the appended claims.

We claim:

I. In an easy opening container, a panel, an integral opening panel part defined by a weakening line of material formed in said panel and joining said panel part to an adjacent part of said panel, said panel part being offset relative to said adjacent part in a direction generally normal to the plate of said panel a distance less than the thickness of the material of said panel, and the thickness of said material along said weakening line being substantially equal to the thickness of the material of said panel less the amount of said offset.

2. The easy opening container of claim 1 wherein the width of said weakening line is generally equal to the thickness of said panel.

3. The easy opening container of claim 1 wherein said weakening line has first and second surfaces, said first surface being coplanar with a surface of said panel adjacent part, and said second surface being coplanar with a surface of said opening panel part.

4. The easy opening container of claim 3 wherein the width of said weakening line is generally equal to the thickness of said panel.

5. In an easy opening container, a panel, an integral opening panel part defined by a weakening line of material formed in said panel and joining said panel part to an adjacent part of said panel, said panel part being offset relative to said adjacent part in a direction generally normal to the plane of said panel a distance less than the thickness of the material of said panel, and the thickness of said material along said weakening line being substantially equal to the thickness of the material of said panel less the amount of said ofi'set, said weakening line having first and second surfaces, said first surface being coplanar with a surface of said panel adjacent part, said second surface being coplanar with a surface of said opening panel part, and said weakening line merging into at least one of said panel parts along a sloping surface.

6. The easy opening container of claim 1 wherein said panel part is offset outwardly of said container relative to said adjacent panel part.

l I I 

1. In an easy opening container, a panel, an integral opening panel part defined by a weakening line of material formed in said panel and joining said panel part to an adjacent part of said panel, said panel part being offset relative to said adjacent part in a direction generally normal to the plate of said panel a distance less than the thickness of the material of said panel, and the thickness of said material along said weakening line being substantially equal to the thickness of the material of said panel less the amount of said offset.
 2. The easy opening container of claim 1 wherein the width of said weakening line is generally equal to the thickness of said panel.
 3. The easy opening container of claim 1 wherein said weakening line has first and second surfaces, said first surface being coplanar with a surface of said panel adjacent part, and said second surface being coplanar with a surface of said opening panel part.
 4. The easy opening container of claim 3 wherein the width of said weakening line is generally equal to the thickness of said panel.
 5. The easy opening container of claim 3 wherein said weakening line merges into at least one of said panel parts along a sloping surface.
 6. The easy opening container of claim 1 wherein said panel part is offset outwardly of said container relative to said adjacent panel part. 